Latest / The Indie Hacker Podcast with Fexingo: Solo Developers, SaaS Side Projects, and Independent Tech / How a Solo Dev Built a SaaS With One API Integration
Transcript
- Lucas: So today I want to talk about a strategy that feels almost too simple for how well it can work — building an entire SaaS around a single API integration. Luna: Like, one integration? Not a whole platform with multiple connections? Lucas: Exactly. One deep, focused integration with a major platform — think Stripe, Shopify, Slack, maybe GitHub. And I have a specific case in mind. There’s a solo developer named Marcus who built a tool called Refundly. It started as a side project to help Shopify merchants automate refunds. That was the whole product. One integration with Shopify’s API. He launched it in late 2024, and by mid-2025, he was at $15,000 a month in recurring revenue. Luna: Wait — $15K MRR from just refund automation? That’s a pretty narrow use case. Lucas: Right, and that’s exactly the point. He didn't try to build a general e-commerce tool. He looked at the Shopify app marketplace, saw that refund management was a pain point for stores doing high volume, and he built a single-purpose tool that integrated with Shopify’s API to handle it. No inventory tracking, no shipping labels. Just refunds. Luna: So the bet was that the integration itself would be the moat. If you’re deep enough into Shopify, it’s harder for a general tool to compete because they’d have to match your integration depth. Lucas: Exactly. And that’s the key insight. When you build around one API, you can become the best at that one thing. You understand every endpoint, every edge case, every rate limit. Marcus told me he spent the first month just reading Shopify’s API docs and testing refund scenarios — partial refunds, multi-currency, gift card returns. By the time he launched, his tool handled cases that Shopify’s own native refund system couldn’t. Luna: That’s the kind of depth that comes from singular focus. But isn’t it risky to bet everything on one platform? What if Shopify changes their API or builds the feature themselves? Lucas: It is a real risk, and I think that’s the trade-off. But what’s interesting is that for solo developers, the risk of building a general product with no integration depth is often higher — because you end up competing with teams that have more resources. With a single integration, you’re targeting a very specific pain point within an existing ecosystem. The users are already there, they already trust the platform, and they’re looking for add-ons. Luna: So the distribution is built in. You list on the platform’s app store, and you get organic discovery from users who are already in the ecosystem. Lucas: Exactly. Marcus told me his first 100 customers came entirely from the Shopify app store. He didn’t run a single ad. He just had a solid listing with good screenshots and a clear value prop. And because his integration was deep, the reviews were positive. That’s the flywheel. Luna: I’ve seen similar stories with Slack integrations. There’s a tool called Standuply that started as just a Slack bot for daily standups. It’s not a huge business, but it’s been around for years making decent MRR. Lucas: Yeah, and that’s another good example. The Slack API is well-documented, and there are thousands of companies using Slack who want a little more functionality. The thing is, you don’t need to be the next Salesforce. You just need to serve a niche that’s underserved within that ecosystem. Luna: What about the technical side? How do you even start with a single API integration as a solo dev? Lucas: Great question. Most major platforms have excellent developer documentation and sandbox environments. You can build and test without affecting real users. Marcus said he used Shopify’s partner dashboard to create a test store, then built the integration using their REST API. He’s a full-stack developer, but he said the hardest part wasn’t the code — it was understanding the refund logic from a business perspective. Luna: So you need domain knowledge in the specific problem you’re solving, not just API skills. Lucas: Right. The tech is the easy part. The hard part is knowing what refund scenarios actually matter to merchants. That’s where the real value is. And because he only had one integration, he could iterate quickly based on customer feedback. He added support for partial refunds and automatic tax recalculation within two weeks of launch because a few users asked for it. Luna: That’s a huge advantage over a team that has to coordinate across multiple integrations. A solo dev can turn around features in days. Lucas: Exactly. And the economics are pretty compelling too. Marcus’s only recurring costs are server hosting and the Shopify API usage. He’s on a cheap VPS, maybe $20 a month. So at $15K MRR, his margins are enormous. Plus, he has no customer acquisition cost because of organic discovery on the app store. Luna: But what about the risk of the platform changing the API or building the feature? I remember when Twitter changed their API rules, it killed a lot of third-party clients. Lucas: That’s the nightmare scenario. And it’s why you need to be careful about which platform you choose. You want a platform that’s big enough to have a thriving app ecosystem, but not so volatile that they’ll break things without notice. Shopify and Slack are generally good — they’ve had stable APIs for years and they rely on third-party developers. Marcus told me he actually worries about Shopify building native refund automation, but he thinks it’s unlikely because it’s a niche feature that most merchants don’t need. Luna: So you’re betting that the platform will stay focused on the core product and leave the edge cases to you. Lucas: Yeah. And you can also mitigate risk by not putting all your eggs in one basket over time. Marcus is now looking at adding a Stripe integration for payment-level refund reconciliation. That gives him a second leg. But he started with one, and that focus is what got him to $15K. Luna: It’s a good lesson for indie hackers who feel overwhelmed by the idea of building a full platform. Start with one API, solve one problem really well, and let the ecosystem do the marketing for you. Lucas: Exactly. And you don’t need to be a genius programmer. You just need to pick the right niche and integrate deeply. There are probably hundreds of opportunities like this in every major API ecosystem. Things like automated invoice generation for QuickBooks, or custom reporting for Google Analytics. Small, focused, and deeply integrated. Luna: Speaking of the ecosystem — if you’ve gotten value from conversations like this, it’s worth considering that listener support is what keeps these episodes coming. A couple of dollars a month genuinely helps cover the hosting and coffee that fuel this show. Lucas: Yeah, it’s a small thing that makes a real difference. If you’ve ever built something or learned something from our episodes, buying a coffee is a great way to say thanks. That’s at buy me a coffee dot com slash fexingo. Luna: And we don’t run ads, so it really is listener-powered. Anyway, back to the topic — one thing I want to dig into is how you actually find the right API to build on. Any advice there? Lucas: Yeah, I think you start by looking at pain points you’ve experienced yourself. Marcus was a Shopify store owner for a side business, so he knew the refund problem firsthand. But if you don’t have that, you can browse app stores and look for categories with lots of low-rated apps — that’s a signal that existing solutions are bad. Then you pick one and build something better. Luna: So it’s almost like you’re reverse-engineering a product from the gaps in a platform’s ecosystem. Lucas: Exactly. And you want to avoid the most crowded categories like email marketing or analytics — those have too many players. Look for niches where there are maybe three or four apps, all with mediocre ratings. That’s where a solo dev can win with a deep integration and great customer service. Luna: What about the pricing model? Marcus is subscription-based, right? Lucas: Yeah, he charges $29 a month for the basic plan, which covers up to 500 refunds. There’s a $99 plan for unlimited. It’s simple, and it aligns with usage. He told me he considered a per-refund fee, but decided against it because merchants prefer predictable costs. Luna: That makes sense. And since his costs are fixed, the margins are great at scale. Lucas: Right. And the beauty is that he’s not fighting for attention on Google Ads or social media. His customers are already on Shopify looking for apps. He just needs to be the best refund app in the Shopify ecosystem. Luna: I think that’s the key takeaway for any solo dev listening: you don’t need to build the next unicorn. You just need to find a platform with a hungry user base and solve one problem better than anyone else. Lucas: Exactly. And if you do that, you can build a sustainable, profitable business that funds your lifestyle. That’s the indie hacker dream, right? Luna: For sure. Thanks, Lucas. Great episode. Lucas: Thanks, Luna. And thanks to everyone listening. See you next time.